Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond annotations (readOnlyHint, openWorldHint, non-idempotent, non-destructive), it discloses that this is a real Chrome where the user is already signed in, that the URL reuses the site's open tab else opens a new one so the user's tabs are preserved, and what the call returns (visible elements and text, with 'the same numbers'). It does not cover failure/auth-expiry behavior, which keeps it at 4.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

It is front-loaded with the core action and constraint, and the tab-behavior and return-value sentences both add information. The trailing Fortnox action list is useful routing context but slightly bloats an otherwise tight definition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description helpfully states what the call answers with, and it explains the tab side effects a caller must anticipate. Remaining gaps are minor (error handling, whether a prior session must exist), which the readOnly/openWorld annotations partly offset.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, including a detailed note on when to omit `app`, so the schema already carries most parameter meaning. The description adds only the tab-targeting behavior of `url`; it says nothing about `app` itself, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb and resource ('Starts the user's Cloud Browser ... and opens `url`') and scopes it against the navigate/other browser siblings with 'Call it first.' An agent can tell immediately that this is the session-initializing open step rather than a mid-session navigation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives clear sequencing guidance ('Call it first') and explains the default target-tab behavior, which tells the agent when this is the right entry point. It stops short of explicitly contrasting itself with cotlet_browser_navigate for already-open sessions, so it is strong but not fully exhaustive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.